Arlen Ness Big Sucker II Compatibility

I want to put a Big Sucker II on my '09 FLHR that has the 103" upgraded cylinders and pistons, with stock heads. i.e., I didn't have the Screaming Eagle heads put in. The breather is compatible with 103" diecast heads. Can someone advise if the heads would be diecast? How would I tell by looking?